Kallstrom, 31, who has made 108 appearances for Sweden, joined the Gunners on transfer deadline day -- and Arsenal's decision to go ahead with the move despite his injury raised eyebrows.

But Wenger, speaking after the 2-0 home win over Crystal Palace that put the Gunners back on top of the Premier League table, told Sky Sports 1: "We have to establish the real truth about this story.

"The earliest he could be available would be the end of February and the latest would be mid-March.

"He arrived here, and fell on his back two days before. First of all, it's very difficult to identify a player, who can come in, of that stature and then we made a medical [check] of his back and we found out he had a little micro-fracture. We have all played with micro-fractures.

"Then Spartak Moscow accepted to share the costs -- as long as he's injured they will pay -- and we had a decision to make. We could take nobody or Kallstrom and it went through on Friday at five o'clock."

Arsenal sealed their win over the Eagles thanks to two goals from Alex Oxlade-Chamberlain, with the man of the match saying: "It's something I want to add to my game -- more goals -- so it was nice to get two today.

"It's always an amazing feeling to score a goal and especially at a stadium like the Emirates, and I'm glad I can help the team with two goals.

"It was a tough game against Palace, and they made it hard for us in the first half. But in the second half we knew if we kept the tempo up and kept wearing them down then we'd get more opportunities, and we did."